#0B71B2

CSS

:root {
  --french-blue: #0b71b2;
  --french-blue-rgb: 11 113 178;
  --french-blue-oklch: oklch(0.531 0.131 245.3);
}

.element {
  color: var(--french-blue);
  background-color: hsl(203 88% 37%);
  border-color: oklch(0.531 0.131 245.3);
}

Tailwind CSS v4

@theme {
  --color-french-blue: #0b71b2;
  --color-french-blue-50: #d8faff;
  --color-french-blue-100: #c6edff;
  --color-french-blue-200: #a7daff;
  --color-french-blue-300: #7fbef7;
  --color-french-blue-400: #55a5e7;
  --color-french-blue-500: #238cd6;
  --color-french-blue-600: #2177b5;
  --color-french-blue-700: #1b5f91;
  --color-french-blue-800: #0c466c;
  --color-french-blue-900: #08314c;
  --color-french-blue-950: #001d32;
}

SCSS

$french-blue: #0b71b2;
$french-blue-rgb: 11, 113, 178;
$french-blue-light: mix(#fff, $french-blue, 20%);
$french-blue-dark: mix(#000, $french-blue, 20%);

.element {
  color: $french-blue;
  box-shadow: 0 0 0 2px rgba($french-blue, 0.35);
}